For decades, orthodontic appliances for use in the straightening of a patient's teeth have, for a given dental arch, been formed of an elastic metal orthodontic archwire and a plurality of orthodontic brackets, each secured to one of the patient's teeth and to which the archwire is connected. Typically, an orthodontic bracket standard in the field has included a base, or pad, that is secured to the tooth and an archwire support, fixed to the pad and containing an archwire slot, of rectangular cross-section, into which the archwire is fit.
Prior to the 1960s, orthodontic archwires had been literally ligated or tied to the brackets, usually with a strong though plastically bendable wire. The ligating of the wire to the brackets involved the meticulous manipulation of the fine wire by the orthodontist using a pliers, and then the cutting of the ligature wire, and the tieing of the ends of the wire so as to securely attach the archwire to the bracket and so as to prevent the sharp wire ends from injuring the patient. Because of the unpleasantness to the orthodontist and the patient of the ligating process, orthodontists have, for many years, desired a "ligatureless bracket" that would replace the ligating process.
True ligatureless brackets have been envisioned as brackets with reusable, non-removable spring clips of one sort or another to fix the archwire to the brackets. In their implementation, true ligatureless brackets have not been successful in performance or in the marketplace for several reasons, most relating to unsatisfactory clinical function, reliability and technique modifications that these brackets require.
Since the 1960s, a urethane doughnut or O-ring like ligature has had widespread acceptance. Such a ligature is radially expanded with a plier tool and snapped around four hooked ends of the tie wings of a double winged bracket and over an archwire set in the slot of the bracket, thereby tightly urging the archwire into the bracket slot and ligating the archwire to the bracket. While not totally eliminating the ligature, the urethane doughnut performed the function of the former ligature without requiring the twisting, cutting or tucking-in of the sharp ends of the ligating wire.
Nonetheless, the current urethane doughnut ligature and double tie-wing bracket is less than totally ideal in several respects. First, in many applications the tie-wings of the brackets interfere with occlusion. Further, they have a limited latitude of placement on the teeth, leave a great deal of room for improvement in aesthetic appearance, and present moderate difficulty in maintaining hygiene. Additionally, differences in designs of the tie-wing brackets for different teeth of a patient can require the orthodontist to stock and match ligatures of different sizes and properties to respective individual brackets. Therefore, there is a need for improvement in the art of ligating orthodontic archwires to brackets and in the overall design of the brackets and the archwire securing structure.